Here’s Pi In Your Eye – HUD Goggles

[John Ohno] has found what is perhaps the best possible use for steampunk goggles: framing a monocular display for a Raspberry Pi-based wearable computer. [John]’s eventual goal for the computer is a zzstructure-based personal organizer and general notifier. We covered [John]’s zzstructure emulator to our great delight in July 2011. Go ahead and check that out, because it’s awesome. We’ll wait here.

[John] has been interested in wearable computing for some time, but is unimpressed with Google Glass. He had read up on turning head-mounted displays into monocular devices and recognized a great opportunity when his friend gave him most of an Adafruit display. With some steampunk goggles he’d bought at an anime convention, he started on the path to becoming a Gargoyle. He encountered a few problems along the way, namely SD card fail, display output issues, and general keep-the-parts-together stuff, but came out smelling like a rose. [John] has ideas for future input additions such as simple infrared eye tracking, the addition of a chording keyboard, and implementing a motorized glove for haptic learning. 

Want to make your own wearable display but have an aversion to steampunk? Check out this homebrew solution with (mostly) 3-D printed frames. And it has servos!

[Thanks John]

7 thoughts on “Here’s Pi In Your Eye – HUD Goggles

    1. I’ve tried modifying existing displays for head mounting in the past. It’s not easy. Displays intended for human-readability at normal focal lengths tend to be too heavy to comfortably strap to your head at any distance, and the torque on your skull is greater the further away it is; if you’re good at math and very neat, you can mount some expensive optics to lower the focal distance to make it possible to make the display closer, but there’s a limit to how much of (say) a cell-phone screen you can get into your visual field without massive distortion at a distance of an inch or two, regardless of what optics you use.

      You might be able to get a projector display and hack that with some optics to get a display that’s usable (and on the face of this, it seems like a good idea — projectors tend to have VGA, HDMI, DVI, and RCA support, and they tend to support very good resolution), but half-decent projectors are even more expensive than HMDs and more difficult to hack. Some portable televisions historically had tiny projection displays, back before high-resolution color LCDs were cheap, but with projection displays you also want to be careful about brightness. In the end, a working projector is $200-$400, and a head-mounted display (albeit at a low resolution) is $100.

      I feel you on this, though. If I had to buy the sacrificial display, I wouldn’t have disassembled it (I actually have had a functional HMD for several years that, for various reasons, hasn’t been particularly useful; I’ve avoided disassembling it because it cost me something like $200). The only reason I even attempted this is that a friend with higher income and lower impulse control sent me an already partially disassembled HMD that was missing a few parts, free.

      The display isn’t what I consider the most interesting part of the project, but it’s the part that was most recently finished when I wrote it up. The more interesting element may be the vibrating motor glove as an output device, but that’s not finished yet.

      1. Well, seems like I need a friend with high income and low impulse control too :D
        What I tried so far are two camcorder viewfinders with tiny CRTs, but one has terribly distorted picture and misses its optics, and I can’t get the other one to display any picture.
        Thanks for your extensive reply, I didn’t want to play down your project.
        As I did not get the viewfinders to work and the only other HMD I have tried out is the Oculus Rift, how good is the picture with your display? Is it distorted, can you see the pixels? Would it be good enough to view the RasPi camera’s feed with it (if you have one)?

        1. The picture is small and slightly blurred at the edges, probably just because of the low resolution of the display. Over all, it’s only slightly less focused than the original HMD (which surprised me, since I didn’t do any of the calculations — I got lucky having the optics be just good enough by flipping over the lens). I could look through the camera, definitely — I was busy using IRC on it this morning, and that was doable with size 20 font — but it’s definitely not a good enough resolution or covering a large enough portion of the eye to be immersive.

          I wish you luck with the viewfinders — I haven’t been able to look into that, but it was always one of the possibilities. Are the two viewfinders of the same (or a similar) type? You could probably try taking the optics out of the dead one and sticking them on the live one. Alternately, if you’re just getting a fish-eye effect on something otherwise in focus, you might try experimenting with whatever lenses you have around (you might get lucky!)

          Another thing you might look at (if you can find a display that’s just barely too big to mount in front of your eye, but not too big to mount on the side of your head) is roof prisms & porro prisms. Some binoculars use these for dealing with the horizontal distance between the objective lenses and the eyepieces (look for the telltale triangular joints), but some of them have porro or roof prisms that are slightly warped to provide magnification. The idea of a porro prism is that you have a (right-triangle) triangular prism and if you look through any side of the triangle, you see a superimposition of the other two sides (I suspect they are used in laser beamsplitting, but if you block off light to one of the sides it ends up looking fairly reflective). I *think* that the prism used in Glass is some variation on a porro prism.

          Back in the day, when I had no money and lower standards and nobody willing to send me expensive consumer electronics, I looked into homebrewing an eye-mounted persistence of vision display based around an LED bar graph display (which is probably still feasible — the PrivateEye was based on this technology, and the Nintendo VirtualBoy actually licensed the device from PrivateEye and used some optics to add parallax); it’s still cheaper, but it’s fairly difficult (find a tiny motor and try to get it to oscillate a bunch of LEDs really fast and then bounce it off a mirror — then try to make sure it doesn’t vibrate enough to move the whole display or screw up the picture or give you a headache, and then make sure it’s small enough and light enough to strap to your head), and unless you have a second actuator for extending the height (I’m assuming that the display is oscillating side to side) you’re stuck with a single bar-graph-display’s height worth of pixels (the ones I got from RadioShack back then were only five or six pixels tall). Hack-A-Week had a project to build a laser oscilloscope with a pair of voice coils, a laser pointer, and a piece of mirror (and you can duplicate this and build a vector display — don’t use a laser if you want to point it at your eye, obviously) but you’ll have a hard time handling the vibrations in a portable head-mounted unit. All of these solutions are cheaper but much more work, much more prone to error, and objectively worse in terms of features (monochrome, limited resolution). As hacks, they are superior because they require more cleverness, but unless you have professional equipment and quite a bit of skill they are almost exercises in bitty-box ingenuity, like doing 3d graphics on a VIC-20 or building a modular synth entirely out of vacuum tubes or writing anything in malboge.

          In an ideal world, we’d have crisp, high-definition, full-color head-mounted laser vector displays that won’t glitch even if you whack it repeatedly with a baseball bat while riding a motorcycle through a gravel pit, and I’m sure that in theory it can be done, but the market hasn’t really been there for professionals to do the pure R&D for it. (Note to HaD readers who work with lasers, optics, and acoustic dampening systems professionally: if you perfect this, I will be very happy and Jeff Minter probably will be too, and you might make a lot of money on it from retro-cyberpunk fanatics.)

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